The ulcus-syndrome in cod (Gadus morhua). V. Prevalence in selected Danish marine recipients and a control site in the period 1976--1979.

The ulcus-syndrome in cod occurred in marine recipients receiving effluents from sugar and cellulose factories. The mean percentages in the years 1976--77 were for Køge, Assens and Nykøbing F. 10.8%, 31.5%, and 7.4%, respectively, while two among 4,211 were affected at the control site, Hundested (Fig. 2). The disease was most prevalent in autumn (Fig. 3) and the primary stages 1 and 2 with papules and erosions were dominating (Fig. 4). One to two year old cod were most frequently attacked by the diseases, but without any significant decrease in condition factor. On the contrary fish with traumatic injuries had a significant lower condition factor than controls (Table II and III). During autumn's 1976-79, 19,238 cod were examined. The mean values for the prevalence of the ulcus-syndrome in Køge, Assens and Nykøbing F. were 12.5%, 41%, and 8%, respectively, while the variations were from 4-20%, 20-48%, and 0-17%, respectively. The problem was negligible at the control site (Table IV). The discussion concerns some aspects that might be of importance for evaluating this pathobiological parameter for use in biological effects monitoring.